1. Field of the Invention
This invention relates to an interaxle differential system for connecting two driven axles of a motor vehicle, which differential system comprises an interaxle differential having two output shafts and also comprises a planetary gear train having three torque-transmitting members which have parallel axes and two of which are operatively connected to respective ones of said output shafts, and restraining means for restraining the third of said torque-transmitting elements against rotation.
2. Description of the Prior Art
Means for restraining a differential of a motor vehicle are known, e.g., from European Patent Specification No. 160,671. In that known arrangement a planetary gear train is provided, which has three torque-transmitting elements and constitutes a conventional differential having a housing which is operatively connected by a worm gear train to a servomotor. As the worm gear train is self-locking, it constitutes means for restraining the rotation of the third torque-transmitting member. But in that case the restrainable differential does not constitute an interaxle differential connecting two driven axles of a motor vehicle but serves as a stearing gear train which under the control of the servomotor constrains the restrainable differential to rotate its two output shafts at different speeds. Besides, in the known arrangement the two output shafts of the differential are connected to the torque-transmitting members of the associated planetary gear train by spur gear trains having the same transmission ratio or gears of equal size and an idler gear for reversing the sense or rotation is required on one side. Particularly in passanger cars the space available may be so confined that it is not possible to accommodate gears equal in size on both sides of the restrainable differential. Another disadvantage of the known arrangement resides in the fact that the servomotor must be operated even when the two output shafts of the unrestrained differential are required to have a desired speed difference. Finally, said two output shafts cannot be entirely released to rotate at any desired speed.
Another restrainable differential for use in a motor vehicle is known from British Patent Specification No. 620,723. In that arrangement a planetary gear train extending in one plane is associated with the differential and comprises three torque-transmitting members, two of which are operatively connected to respective output shafts of the differential whereas a brake is associated with the third torque-transmitting member. That arrangement has the disadvantage that the brake must arbitrarily be actuated by the driver and that that known differential constitutes an interwheel differential between the two wheels of an axle rather than an interaxle differential connecting two driven axles of a vehicle.